This application is a national stage application of International Application No. PCT/SE98/00398, filed Mar. 5, 1998.
Due to the increasing number of individuals having allergical/asthmatic problems the environment debate has been focused around the indoor environment, the central point being the quality of the indoor air. In connection with this focusing the use of so called freestanding air cleaners has increased simultaneously as their function has developed from providing isolated contributions to constituting a complement to an existing ventilation system. However, in order to achieve a complete acceptance as a complement to or part of ventilating measures these devices must fulfill high technical demands, they must be easy to handle and last but not least they must be adaptable to a certain indoor environment through their design and their choice of colour scheme.
In certain indoor environments, i.e. open-plane offices, individuals having a higher demand of clean air may face problems since it costwise, spacewise or from other reasons may be difficult to clean the air in the entire premises in question to fulfill the demands of said individuals.
The technical performance for air cleaners may briefly be summarised as the clean air generation of the device (CADR equivalent clean air generation (m3/h) at extremely low noise level). By low noise level is in practice meant a noise level lower than 35 dbA and preferably lower than 30-31 dbA. The technical development described e.g. in SE-A-920515-6, PCT/SE95/00038, SE-A-9503096-1 and SE-A-9403369-3 has resulted in devices that fulfils the above mentioned required technical performance.
According to the description in the patent applications mentioned above the precipitator may be designed from high-ohmic, preferably cellulose-based material, e.g. paper. The precipitator of paper is of disposable type, i.e. it should be replaced by a new one when polluted. By this arrangement a possibility has been created to design precipitators having a large extension perpendicular to the direction of the air flow through the precipitator, said precipitator having a high capacity at exceptional low pressure drop. In SE-A-9602211-6 precipitators are described that may be manufactured with a suitable diameter of 40-50 cm. If precipitators of such dimensions would be manufactured in a traditional way, e.g. from sheet metal, they would in practice be unwieldy.
A primary object of the present invention is to provide a device for air cleaning, a laminar flow being maintained in said device although the air is passing through the precipitator by the use of pressure.
A further object of the present invention is that the device should have extremely compact dimensions, especially as regards the extension of the device in the direction of the air flow.
Despite the extremely compact dimensions of the device a further object is to provide a clean air flow that in its turn creates a microclimate within a larger indoor area. In order to maintain a high separation degree as regards micro particles for the device according to the invention it is a further object that the air velocity through the precipitator should have as small differences as possible across the cross-section area of the precipitator.
A further object of the present invention is that the air flow through the precipitator, to as large extent as possible, should be laminar. Thereby the space around the user is flushed by a large volume of air having an air velocity below or near to 1 m/s, this being an air flow having a pleasant xe2x80x9cbreezxe2x80x9d -feeling.
A further object of the present invention is that proper charging of the particles in the air flow should occur, said air volumes normally being larger than 200 m3/h and preferably larger than 500 m3/h.
The objects of the invention is realised by a device that has been given the characteristics of the appending claims. Preferred embodiments of the invention are defined in the dependent claims.